الفهرس 
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Abstract
This study assessed the fracture resistance of ceramic inlays of different CAD/CAM ceramic materials using Lithium Disilicate glass ceramic (IPS-EMAX CAD), Zirconia-reinforced Lithuim Silicate (CELTRA-DUO) and hybrid composite filled with Zirconium silicate particles (SHOFU HC BLOCK). Thirty-three extracted intact permanent maxillary first premolar teeth were collected and cleaned. Standardized preparations were done with occlusal box 2mm-deep, a 3.5 mm isthmus width and a divergence angle of nearly 6 degrees. The proximal gingival margin was located 1 mm above the cemento-enamel junction. The width of the proximal box was 3 mm. All of the internal angles were made rounded. All these measurements were surveyed using a periodontal probe. After finishing the cavity preparations, digital impressions of the preparations were taken with CEREC scanner. The software was used to design the inlay restorations. This virtual information was then sent to a milling machine CEREC MCXL where the dental restorations were carved out of the blocks. Teeth were grouped into three groups (n=11); each group was restored with one of the three tested CAD/CAM materials. After cementation of the inlays with dual cure self adhesive resin cement, all specimens obtained were stored in distilled water at room temperature for 24 hours prior to testing. They were submitted in a Universal Testing Machine until fracture and the fracture loads (N) were measured. The compressive load was applied by a 4mm steel wedge at the central fissure of the premolars at a 0.1 mm/min cross-head speed until fracture. Results were statistically analyzed by ONE WAY ANOVA test analysis. The mean value of the fracture resistance test showed higher value for IPS Emax CAD (1104.627) followed by the Celtra Duo (937.024) and then followed by the Shofu HC (724.417) respectively.
A statistical significant difference was found in the fracture resistance among the three studied groups, ANOVA TEST (F=5.905, p=0.007). Comparison between the three studied groups revealed that, there was a stastistical significance between IPS EMAX CAD and SHOFU HC: Difference=380.210, p=0.005. It was concluded that Strengthening of the glass ceramic material nor of the composite resin with zirconia particles had a positive influence on the fracture resistance of the materials.